I think you should learn your pokemon strength and use it against the holes.
I just think that,because alot of people say that.
Chat with our AI personalities
it is in the same place where you would find any other important hole.
you will go to lavaridge town again from cablecar and then go to south the ground will shake and there will be a hole and you will enter the magma hideout
there are no Pokemon in the dotted hole all there is are the sapphire
You can find it in the top floor in Mt. Pyre just go down the stairs near the hole that makes you fall through the floor. There should be a Poke Ball thingy containing TM30(Shadow Ball).
Head west of Fallarbor Town, and there will be a house at the end of the tan dirt path. That is the Fossil Maniac's house. Inside, talk to his little brother next to the hole in the back and he will give you TM 28, Dig.